Single integrated services digital network (ISDN) lines provide an intermediate solution for users in need of digital services having a capacity greater than that of conventional telephone subscriber lines, but less than that of a T1 connection. A single basic rate interface line (BRI line) has two B-channels. Each B-channel is capable of supporting a voice connection with advanced features such as conference calling. Other examples of advanced features are call forwarding, call transfer, auto callback, and privacy. Auto callback causes the switch to call a party back if the first attempt to call the party indicated that the called party's line was busy. The second call is placed as soon as the switch determines that the called party's line is now free. "Privacy" is a feature utilized in EKTS systems to prevent other members of an EKTS group from listening to a call placed by one of the members. The specific features available on any ISDN line vary depending on the switching system.
ISDN networks are configured under the assumption that the phone is "dumb" with respect to the implementation of the advanced features. The phone is assumed to contain only the intelligence necessary to report key strokes to the central office switch, lights LEDs on the handset, and display messages on an LCD or similar display. The available keys on the phone are numbered. When a key is depressed, the key number is sent to the switch.
The advanced features are implemented by assigning features to specific keys. The specific key assignments vary from switch to switch. In addition, any particular switch may implement several different telephone configurations corresponding to the various phone models that were anticipated when the switch was programmed. When a user subscribes to an ISDN service, a set is chosen depending on his or her equipment. In the current implementation, the user must ask the telephone company for the Feature Identification Number value for each feature, i.e., key number, and note that information on the telephone.
In principle, the telecommunications switch manufacturers and/or telephone companies could standardize the keys used for advanced features. However, the existing installed base of non-standard ISDN telephones makes such standardization difficult.
There are a limited number of keys on the telephone. In addition to implementing the advanced features, these keys are also used for speed dialing and other local features such as mute, speaker, etc. Currently available ISDN telephones do not provide any means for moving the advanced features so that the user can arrange his or her speed dialing or other local keys in a manner that is more optimum for the user.
Another problem with prior art ISDN telephone advanced features is the number of key strokes needed to exercise some of the features. For example, to set up a conference call, the user must typically perform 6 actions. First, the user dials the first party. Second, the user presses the conference key. Third, the user must wait for a "conference" LED to turn on. Fourth, the user presses another key and waits for a dial tone. Fifth, the user dials the second telephone number. Finally, the user presses yet another key, "retrieve to conference", to complete the connection between the user and the two external parties to the call. In principle, the user needs only dial the two telephone numbers and press one key to set up a conference call; hence, this procedure is obviously much more cumbersome than it needs to be.
Broadly, it is the object of the present invention to provide an improved ISDN phone.
It is a further object of the present invention to provide a method and telephone that allows all switches to implement a standard set of keys for the ISDN advanced features.
It is yet another object of the present invention to provide a method and telephone that does not require the user to identify the keys to be used for the advanced features.
It is a still further object of the present invention to provide a telephone that reduces the number of key strokes needed to utilize the advanced features.
It is yet another object of the present invention to provide a telephone that allows the user to customize the keys.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.